Part of object and texture colour not rendering properly, lamps beside sun does not work
there are several things that went wrong:


no lamp other than the sun working:
thats indeed due to the fact that your frame is 400 m wide. Lamps in Blender (as in the real world) have a quadratic light falloff. so the strength is dependent on the distance from the lamp and your object. if you want to have light from 500m away, the strength must be something like (insert a really high value here).
The sun doesn't have a falloff in blender as it has no real location, it's just a directional light source.
Your image plane is not a plane. it has 8 vertices and the faces overlap each other. 
go into edit mode with TABface select (shift + TAB) select the front face and delete it ( X > Faces)